Forced cooling rotary electric machine

ABSTRACT

The invention aims at providing a forced cooling rotary electric machine capable of bringing temperature distribution close to a designed temperature distribution and avoiding becoming a larger size, and employs a wedge formed with ventilation grooves and a wedge not formed with the ventilation grooves to regulate the flow rates of cooling gas passing through air ducts, so that the cooling gas supplied to a part of a stator core, in which temperature is low, can be caused to flow positively to a part in which the temperature is high and the temperature distribution in the axial direction of the stator core can be uniformized. As a result, the temperature distribution in the axial direction of the stator core can be brought close to a designed temperature distribution, and a forced cooling rotary electric machine that need not be made larger in size with a margin can be obtained.

BACKGROUND OF THE INVENTION

The present invention relates to a forced cooling rotary electricmachine configured so that cooling gas is caused to flow forcedly by aself-cooling fan provided on a rotating shaft or a separate type airblower to cool internal equipment in the rotary electric machine such asa turbine generator and an electric motor. More particularly, it relatesto a forced cooling rotary electric machine suitable for cooling astator core that is subjected to a variable magnetic field and isheated.

Generally, to cool a stator core and to uniformize the temperaturedistribution in the axial direction of the stator core (stackingdirection of silicon steel plates), a forced cooling rotary electricmachine in which a plurality of air ducts are provided in the axialdirection of a stator core has already been proposed as shown, forexample, in JP-A-2006-109616 (FIGS. 6 and 7).

In such a forced cooling rotary electric machine, depending on the typeand construction of machine, the temperature distribution in the axialdirection of the stator core is uniformized by changing the ventilationcross-sectional areas of the air ducts while the core stacking pressurebetween the adjacent air ducts is made equal, or the temperaturedistribution in the axial direction of the stator core is uniformized bychanging the core stacking pressure between the adjacent air ducts eachhaving the same ventilation cross-sectional area.

BRIEF SUMMARY OF THE INVENTION

As described above, by changing the cross-sectional areas of the airducts or by changing the core stacking pressure between the air ducts,cooling gas can be distributed in the axial direction of the stator corein a well-balanced manner. The temperature distribution in the axialdirection of the stator core can be thus uniformized to some degree.

However, even for the forced cooling rotary electric machine having beendevised as described above, a ventilation test conducted after theassembly of an actual machine reveals that the temperature distributionas designed initially cannot be obtained because of a difference in flowpath resistance caused by a difference in length of the circulation flowpath of cooling gas, so that satisfaction is scarcely attained. Toenhance the cooling capacity from the initial stage, a forced coolingrotary electric machine having a margin must be designed and used, sothat the forced cooling rotary electric machine inevitably becomes largein size.

An object of the present invention is to provide a forced cooling rotaryelectric machine in which the temperature distribution is brought closeto the designed temperature distribution, by which a larger size thereofcan be avoided.

To achieve the above object, the invention is configured so that a wedgeformed with a ventilation groove and a wedge formed with no ventilationgroove are used to regulate the flow rates of cooling gas passingthrough air ducts.

Since the wedge formed with the ventilation groove and the wedge formedwith no ventilation groove are employed as described above, the wedgewith no ventilation groove is used in the air duct provided in an areaof a stator core where the temperature is low (the air duct in a coolingpath having small flow path resistance) to restrict the flow rate, andby just that much, cooling air can be caused to flow to another air duct(the air duct in a cooling path having large flow path resistance).Also, the wedge formed with the ventilation groove is used in the airduct provided in an area of the stator core where the temperature ishigh (the air duct in the cooling path having the large flow pathresistance), so that the cooling gas can be caused to flow positively.Temperature distribution in the axial direction of the stator core canbe thus uniformized. As a result, the temperature distribution in theaxial direction of the stator core can be brought close to the designedtemperature distribution, and a forced cooling rotary electric machinethat need not be made larger in size with a margin can be obtained.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic longitudinally-sectioned side view showing thevicinity of a stator core of a forced cooling turbine generator that isthe first embodiment of a forced cooling rotary electric machineaccording to the invention.

FIG. 2 is a perspective view showing a wedge used in the firstembodiment.

FIG. 3 is an enlarged perspective view showing a part of a stator usingthe wedge shown in FIG. 2.

FIG. 4 is a perspective view showing another wedge used in the firstembodiment.

FIG. 5 is an enlarged perspective view showing a part of the statorusing the wedge shown in FIG. 4.

FIG. 6 is a partially-broken perspective view showing an appearance ofthe forced cooling turbine generator of FIG. 1.

FIG. 7 is a diagram showing temperature distribution in the axialdirection of the stator core according to the first embodiment.

FIG. 8 is a longitudinally-sectioned front view of a stator, showing thesecond embodiment of a forced cooling rotary electric machine accordingto the invention.

FIG. 9 is a longitudinally-sectioned side view of a stator, showing thethird embodiment of a forced cooling rotary electric machine accordingto the invention.

FIG. 10 is a longitudinally-sectioned side view of a stator, showing thefourth embodiment of a forced cooling rotary electric machine accordingto the invention.

FIG. 11 is a perspective view showing a modification of a wedge used inthe forced cooling rotary electric machine according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The first embodiment of the forced cooling rotary electric machineaccording to the invention will now be described based on a forcedcooling turbine generator shown in FIGS. 1 to 6. The forced coolingturbine generator shown here is a forced cooling turbine generator inwhich a cooling gas is circulated in the machine without using outsideair, and cooling is made in such configuration regardless of the kind ofcooling gas.

As shown in FIGS. 1 and 6, the forced cooling turbine generator 1 isgenerally comprised of a rotor 3 formed on a rotating shaft 2, a stator4 provided at the outer periphery of the rotor 2 with a gap G beingprovided therebetween, an end frame 6 supporting the rotating shaft 2via bearings 5, a stator frame 7 fixed to the end frame 6 and supportingthe stator 4, and a housing 7H covering the stator frame 7 to form anenclosed structure together with the end frame 6.

Fans 2F are respectively provided on both sides of the rotating shaft 2with the rotor 3 held therebetween, as shown in FIG. 1, fans 2F areprovided. By these fans 2F, the cooling gas is introduced into the gap Gbetween the rotor 3 and the stator 4, and is supplied toward the centralpart side in the axial direction of the rotor 3.

Although not shown in the figures, the rotor 3 has a field core and afield winding wound around the field core and forms a plurality ofmagnetic poles in the circumferential direction.

The stator 4 is comprised of a stator core 8 that is formed by stackingsilicon steel plates in the axial direction of the rotating shaft 2 andby clamping the lamination ends with end clamps 8E, a plurality ofU-shaped winding grooves 9 that each have a depth increasing from theinside of the stator core 8 toward the outside thereof, are formedentirely along the stacking direction of the stator core 8, and areformed at equal intervals in the circumferential direction, a statorwinding 10 incorporated in the winding grooves 9, and a wedge 11 that isdriven in a wedge groove 9W formed on the opening side of each windinggroove 9 to fix the stator winding 10 in the winding groove 9.

The stator core 8 is formed with a plurality of air ducts 13 that leadfrom the inside to the outside with duct spacers 12 (FIG. 3) beinginterposed between the stacked silicon steel plates every apredetermined number of sheets to perform cooling. These air ducts 13are formed at equal intervals, and packets 8P, each of which is thestacking unit of silicon steel plates positioned between the air ducts13, are formed so as to each have the same thickness.

Further, on the back surface side (outside diameter side) of the statorcore 8, partition walls 14 are provided every a plurality of packets, bywhich ventilation zones 15A1, 15A2 that allow the cooling gas to flowfrom the inside to the outside diameter side and ventilation zones 15Bthat allow the cooling gas to flow from the outside to the insidediameter side are formed alternately in plural numbers.

The stator 4 of the forced cooling turbine generator configured as aboveis cooled as described below. The cooling gas pressurized by the fans 2Fis introduced into the gap G between the rotor 3 and the stator 4, andis supplied toward the center side in the axial direction of the gap G.In the air ducts 13 opposed to the ventilation zones 15A1, 15A2, thecooling gas flows from the inside to the outside, and flows to the backsurface side of the stator core 8. From there, the cooling gas reachesthe fans 2F via a cooler, not shown. On the other hand, in the air ducts13 opposed to the ventilation zones 15B, the cooling gas pressurized bythe fans 2F is introduced to the back surface side of the stator core 8via air ducts, not shown. From there, the cooling gas flows from theoutside to the inside of the air ducts 13, and reaches the air ducts 13of the adjacent ventilation zones 15A1 and 15A2 after passing throughthe gap G. Then, the cooling gas flows from the inside to the outside,reaching the back surface side of the stator core, and from there,reaches the fans 2F via the cooler, not shown.

By the above flowing of the cooling gas, the stator core 8 is cooled.Naturally, in the air ducts 13 opposed to the ventilation zones 15A1close to the fans 2F, a large quantity of the cooling gas flows, and inthe ventilation zones 15A2, 15B distant from the fans 2F, a smallquantity of the cooling gas flows. In other words, a difference in flowrate of cooling gas is caused by the difference in flow path resistanceresulted from the difference in length between circulation flow paths,which are cooling gas flow paths in which the cooling gas flows throughthe fans 2F and the air ducts 13. Such nonuniformity of the flow rate ofthe cooling gas results in nonuniformity of cooling temperature.Therefore, the temperature rise in the central part in the axialdirection of the stator core 8 is remarkable as compared with the bothend parts in the axial direction thereof, and there arises a problemthat a turbine generator must be designed so as to have the maximumvalue of this temperature rise.

In view of the above, in this embodiment, the cooling temperature ismade more uniform by adjusting the nonuniformity of the flow rate of thecooling gas by the wedges 11. Specifically, the circulation flow pathsof the cooling gas passing through the air ducts 13 opposed to theventilation zones 15A1 close to the fans 2F are short and the flow pathresistance is small, and a large quantity of the cooling gas flows inthese air ducts 13. Therefore, to the stator core 8 opposed to theventilation zones 15A1, wedges 11A, which have the same trapezoidalcross section over the total length as shown in FIG. 2, are applied. Asshown in FIG. 3, the wedges 11A facing to the air ducts 13 serve asresistance members, so that the cooling gas flowing in the air duct 13is throttled and its flow rate is restricted. On the other hand, sincethe circulation flow paths of the cooling gas, which pass through theair ducts 13 opposed to the ventilation zones 15A2, 15B distant from thefans 2F are long and the flow path resistance is large, the flow rate ofthe cooling gas is restricted. Therefore, to the stator core 8 opposedto the ventilation zones 15A2, 15B, wedges 11B, which are provided withventilation grooves 11G at positions opposed to the air ducts 13 asshown in FIG. 4, are applied. As shown in FIG. 5, there is no resistancemember facing the air ducts 13, and the flow rate of the cooling gasflowing into and out of the air ducts 13 can be increased. The wedges11A and 11B cooperatively serve as flow path resistance regulating meansfor making more uniform the flow path resistances of the cooling gasflow paths, and also as flow rate regulating means for making moreuniform the flow quantities of the cooling gas flow paths according tothe invention.

As described above, by selectively using the wedge 11A having noventilation grooves and the wedge 11B having the ventilation grooves 11Gfor each of the air ducts 13 opposed to the ventilation zones 15A1, 15A2and 15B, the cooling gas temperature and the temperature distribution inthe axial direction of the stator core could be uniformized as shown inFIG. 7.

More specifically, as shown in FIG. 7, in this embodiment A, by raisingthe temperature at the both end parts in the axial direction and bylowering the temperature at the central part in the axial direction, bywhich the cooling air temperature could be uniformized approximately ascompared with a conventional example B in which the cooling gastemperature is high on the central part side in the axial direction ofthe stator core 8. As a result, according to this embodiment a, thetemperature distribution in the axial direction of the stator core 8could also be uniformized approximately as compared with a conventionalexample b. The conventional examples B and b show the case where theinstallation intervals of air ducts are made large at the both end partsin the axial direction, and made small at the central part in the axialdirection to uniformize the flow rate of the cooling gas. In theconventional examples, by making the installation intervals of the airducts large at the both end parts in the axial direction, the thicknessof a packet 8P, which is the stacking unit of silicon steel plates atthe both end parts in the axial direction is also increased. As aresult, temperature of these parts rises in proportion to the square ofthe packet thickness, and as shown in FIG. 7, the temperature rise atthe both end parts in the axial direction of the stator core isremarkable. In this embodiment a, the thickness of the packet 8P is thesame over the length in the axial direction of the stator core 8, andthe temperature distribution in the axial direction of the stator core 8could be uniformized approximately as the temperature distribution ofthe cooling gas.

As described above, according to this embodiment, since the temperaturedistribution in the axial direction of the cooling gas and the statorcore 8 can be uniformized approximately, the temperature rise of thewhole can be restrained effectively, and also portions where temperaturerises remarkably are eliminated. Therefore, there is no need to increasethe size of the turbine generator so as to give a margin to the coolingcapacity.

In the above-described embodiment, for example, the circulation flowpath of the cooling gas passing through the air duct 13 of theventilation zone 15A1 close to the fan 2F is from the fan 2F and returnsto the fan 2F through the gap G, the air duct 13 and the back surface ofstator core. In the case where all the cooling gas reaching the backsurface side of the stator core 8 is discharged in one direction, forexample, in the upward direction, differences in circulation flow pathlength of cooling gas are caused in the circumferential direction of theair duct 13. Specifically, even in the identical air duct 13, adifference in length of circulation flow path arises between thecirculation flow path of the cooling gas passing through the side closeto the discharge side and the circulation flow path of the cooling gaspassing through the side distant from the discharge side. Naturally, ifthe circulation flow path is long, the flow path resistance increases,and the flow rate of the cooling gas flowing there is restricted.

Accordingly, in the second embodiment of the forced cooling rotaryelectric machine according to the invention, as shown in FIG. 8, in thesame air duct 13, the wedges 11B having the ventilation grooves 11G areprovided on the side where the circulation flow paths of the cooling gasare long, and the wedges 11A having the trapezoidal cross section overthe total length are provided on the side where the circulation flowpaths of the cooling gas are short.

More specifically, in this embodiment, in the case where the dischargedirection of the cooling gas is above the stator core 8, the wedges 11Ahaving the same trapezoidal cross section over the total length are usedin the upper half of the air duct 13 to restrict the flow rate of thecooling gas, and the wedges 11B having the ventilation grooves 11G areused in the lower half of the air duct 13 to increase the flow rate ofthe cooling gas. In other words, the flow path resistance is increasedin the upper half of the air duct 13, and the flow path resistance isdecreased in the lower half thereof, so that the flow rate of thecooling gas is uniformized.

In this embodiment, the case where the cooling air is caused to flowfrom the inside to the outside of the air duct 13 has been explained.Needless to say, this configuration can also be applied to the casewhere the cooling air is caused to flow from the outside diameter sideto the inside diameter side of the air duct 13.

Thus, the flow path resistance in the circumferential direction of theair duct 13 can be changed by using the wedge 11A having no ventilationgrooves 11G and the wedge 11B having the ventilation grooves 11G incombination. As a result, the flow rates of all the circulation flowpaths of the cooling gas are uniformized, and the temperaturedistribution in the circumferential direction of the stator core 8 canbe uniformized.

FIG. 9 shows the third embodiment of the forced cooling rotary electricmachine according to the invention. This embodiment differs from thefirst and second embodiments in that a plurality of air ducts 13A and13B each having a different space are provided in the axial direction ofthe stator core 8. The packets 8P, each of which is the stacking unit ofsilicon steel plates positioned between the air ducts 13A and 13B, havethe same thickness.

Specifically, the space of the air ducts 13A of the ventilation zones15A1 at both end parts in the axial direction of the stator core 8 ismade small, and the space of the air ducts 13B of the ventilation zones15A2, 15B in the intermediate part in the axial direction of the statorcore 8 is made large.

By this configuration, since the flow area of the air ducts 13A close tothe fans 2F is decreased and the flow path resistance of the cooling gasincreases, the flow rate of the cooling gas decreases. Accordingly, thecooling gas can be allowed to flow to the air ducts 13B in theintermediate part in the axial direction. Further, since the flow areaof the air ducts 13B distant from the fans 2F is increased and the flowpath resistance of the cooling gas decreases, the flow rate of thecooling gas increases. As a result, the flow rates of the cooling gas onthe side close to the fans 2F and on the side distant from the fans 2Fcan be uniformized. Therefore, the temperature distribution of thestator core 8 can be uniformized.

In this embodiment, the flow path resistance is changed by changing thespaces of the air ducts 13A and 13B. Further, the wedges 11A and 11B inthe first and second embodiments are used. Therefore, the flow rate ofthe cooling gas flowing in all the circulation flow paths passingthrough the air ducts 13A and 13B can be uniformized more.

As described above, this embodiment can also achieve an effectequivalent to that of the first embodiment.

FIG. 10 shows the fourth embodiment of the forced cooling rotaryelectric machine according to the invention. This embodiment differsfrom the third embodiment shown in FIG. 9 in that gap dimensions of allthe air ducts 13 are made the same, the thickness of a packet 8P1opposed to the ventilation zones 15A1 at the both end parts in the axialdirection of the stator core 8 is increased, and the thickness of apacket 8P2 opposed to the ventilation zones 15A2, 15B is decreased. Inother words, in this configuration, the number of the air ducts 13 ofthe ventilation zones 15A1 at the both end parts in the axial directionof the stator core 8 is decreased, and the number of the air ducts 13 ofthe ventilation zones 15A2, 15B at the intermediate part in the axialdirection of the stator core 8 is increased.

By increasing the number of the air ducts 13 in the ventilation zones15A2, 15B at the intermediate part in the axial direction of the statorcore 8 as described above, the flow rate of the cooling gas isincreased, and thereby the flow rate of the cooling gas of the air ducts13 of the ventilation zones 15A1 at the both end parts in the axialdirection of the stator core 8 can be reduced. As a result, thetemperature distribution in the axial direction of the stator core 8 canbe uniformized.

In this embodiment as well, the wedges 11A, 11B in the first and secondembodiments are used. Therefore, the flow rate of the cooling gasflowing in all the circulation flow paths passing through the air ducts13A, 13B can be uniformized further.

FIG. 11 shows a modification of the wedge used. In the above-describedembodiments, as shown in FIG. 1, the length of the wedge 11A, 11B isalmost equal to the length of each of the ventilation zones 15A1, 15A2and 15B, and the wedges 11A, 11B are selectively used to suit theventilation zones 15A1, 15A2 and 15B.

However, for example, in FIG. 1, when the wedges 11A having the samecross-sectional shape are used for all of the air ducts 13 of theventilation zones 15A1 at the both end parts in the axial direction ofthe stator core 8, if a difference arises in the flow rate of thecooling gas, a wedge 11C having a length L in which a section L1 havingthe same cross-sectional shape and a section L2 having the ventilationgrooves 11G are mixedly provided may be used. Further, a plurality ofsuch wedges 11C having the length L may be provided in each of theventilation zones 15A1, 15A2 and 15B. On the contrary, the wedge 11Chaving the length L may be provided astride the ventilation zones 15A1and 15B and the ventilation zones 15A2 and 15B.

As described above, according to the respective embodiments of theinvention, the flow path resistance of the circulation flow path of thecooling gas, that is, the flow rate of the cooling gas passing throughthe air duct is regulated according to the length of the circulationflow path, in other words, the flow path resistance of the circulationflow path, and the temperature distribution in the axial direction ofthe stator core can be uniformized approximately.

In the above-described embodiments, as the forced cooling rotaryelectric machine, the forced cooling turbine generator has beenexplained as one example. However, it is a matter of course that theinvention can also be applied to a forced cooling electric motor.Further, in the above-described embodiments, the forced cooling rotaryelectric machine in which the cooling gas is circulated within themachine has been explained. However, the invention can also be appliedto an open-type forced cooling rotary electric machine in which outsideair is introduced, and the exhaust gas after cooling is discharged tothe outside of the machine. In the open-type forced cooling rotaryelectric machine, the lengths of the flow paths of the cooling gas froma fan for introducing outside air to an exhaust section via air ductsnaturally differ, and the invention may be applied. Further, in theabove-described embodiments, even if the flow path resistance or theflow rate of the cooling gas is uniformized, in some cases, thetemperature is not necessarily uniformized. In such a case, a flow pathresistance regulating means for uniformizing the temperature of thestator winding incorporated in the winding grooves may be provided onthe side facing to the rotor of the air ducts provided in the statorcore to approximately uniformize the temperature distribution in theaxial direction of the stator core.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A forced cooling rotary electric machine comprising: a rotor formedon a rotating shaft; a stator provided around an outer periphery of therotor with a gap therefrom, said stator having a stator core formed bystacking silicon steel plates along a longitudinal direction of therotating shaft, a stator winding incorporated in winding grooves formedin the stator core, and wedges having a trapezoidal cross section andinserted in opening sides of the winding grooves to fix the statorwinding in the winding grooves, said stator core being formed with aplurality of air ducts in a stacking direction of the silicon steelplates, in which air ducts a cooling gas is forcedly caused to flow,said air ducts being provided at equal intervals in the stackingdirection of stacked steel plates; a plurality of partition walls beingprovided at equal intervals in the stacking direction of the stackedsteel plates on an outer peripheral side of the stator core to form aplurality of ventilation sections, the cooling gas being caused to flowin the adjacent ones of the ventilation sections in reverse directionsto each other, said wedges being formed to have the trapezoidal crosssection and including first wedges formed with ventilation grooves atpositions opposed to the air ducts and second wedges having noventilation grooves, said ventilation grooves being formed to have thesame size in a direction of the rotary shaft as that of said air ductsin a direction of the rotary shaft and said wedges formed with theventilation grooves being formed to have at parts of the ventilationgrooves the same size in a peripheral direction of the rotary shaft as awidth of said winding grooves, so that the wedges present no resistancemember facing the air ducts; and flow path resistance regulating meansfor making more uniform the flow path resistances of flow paths for thecooling gas being formed by arranging the wedges formed with ventilationgrooves on said air ducts in long flow paths for the cooling gas throughthe ventilation sections and the wedges having no ventilation grooves onsaid air ducts in short flow paths for the cooling gas.
 2. The forcedcooling rotary electric machine according to claim 1, wherein therotating shaft is provided with fans on both sides in an axial directionof the rotor.